DALLAS — There was a time when Dirk Nowitzki was a young, rising star, a guy whose expanding skills were making his team more of a championship contender every spring.

Now Nowitzki is at the point in his career where teammates talk about wanting to help him finally win a ring. Having been to the NBA finals and won an MVP award, it's the only thing that still drives him.

His Dallas Mavericks will give it another try starting Saturday night with the opener of a first-round series against the Portland Trail Blazers and LaMarcus Aldridge — a young, rising star whose expanding skills are making his team more of a championship contender.

While skeptics say the Mavs are too old and too flawed to win it all, Nowitzki's rebuttal is simply, "I don't talk to skeptics."

"We're playing for a championship," Nowitzki said Friday. "That's really the only goal. I don't know if we have something to prove. If we don't win a championship, it's another disappointing season."

Dallas Mavericks forward Dirk Nowitzki (41), of Germany, attempts a shot as New Orleans Hornets forward Jason Smith (14) defends in the first half of an NBA basketball game Wednesday, April 13, 2011, in Dallas. (Tony Gutierrez, Associated Press)

Nowitzki knows all about those. Since blowing a 2-0 lead in the 2006 NBA finals, Dallas has won only a single playoff series. The Mavs have been dumped in the first round three of the last four postseasons, fueling much of that skepticism. Portland is the chic pick as the bottom seed most likely to pull off an upset this round.

"We know that a lot of people doubt us, but we also know we can't just talk come out and talk about how good we are or how well we're going to play," Mavs coach Rick Carlisle said. "We're going to have to do it on the floor. That's the way it should be. I don't think I've ever been with a team that didn't feel like we have something to prove every time we step on the floor. Our situation now is no different."

Although the Trail Blazers are a sixth seed, they've been on the rise the last few seasons. The addition of Gerald Wallace at the trade deadline has really sped things up.

Portland is 11-5 since mid-March, with a pair of wins over both San Antonio and Dallas, plus single wins over the Lakers and Oklahoma City.

The Blazers have a nice mix of young and old. They balance 30-somethings starters Andre Miller and Marcus Camby with the 28-year-old Wallace and Aldridge leading a parade of guys in their fifth season or less. That group includes Brandon Roy and Wesley Matthews, who in his second season is the team's second-leading scorer.

They also have lots of size, from big guards who can muscle up on Dallas' backcourt to plenty of long arms to make things tough closer to the rim.

"I think we do a great job with the guys we have in versatility, you know, guys being able to guard different positions," Wallace said. "So instead of up trying to match up with other teams, we put pressure on them to try to match up with us."

Aldridge is the toughest matchup.

The 6-foot-11 power forward averaged 21.8 points and 8.8 rebounds per game this season, both career bests. But his improvement went beyond the numbers. He took on the challenge of fighting for more points in the paint, a great way to earn respect in the NBA. He also thrived in the role as the team's focal point, accepting and embracing that challenge.

"When he gets to the middle and he gets to his sweet spot, he's almost unstoppable," said Mavs center Tyson Chandler, who will have to cover Aldridge. "We've got to make it tough for him, keep him away from easy baskets, force him to roll out, get him to some uncomfortable spots and get him missing some baskets so we can fast break."

Aldridge has been especially tough on Dallas, averaging 27.8 points and 9 rebounds over four meetings. He scored 35 points in a December game he proudly calls his breakthrough performance of the season. A native of the Dallas area, he'll be playing in front of friends and family, including his mother, who is battling cancer and has rarely been able to visit Portland to watch him play in person.